1. Field of the Invention
The present invention relates to an optical fiber wiring sheet having a structure of branching coated optical fibers and used for optical circuit packages, optical circuit devices and other applications pertaining to optical communication and optical information processing, as well as a method of manufacturing the same.
2. Description of the Related Art
As optical fiber wiring sheets that bundle coated optical fibers, optical fiber tape cores have been known. Just like optical fiber cables, etc., optical fiber tape cores are used in applications where coated optical fibers must be stored in small-diameter cables at high density, and are also used for multi-core optical fiber wires connecting devices or components inside devices. Optical fiber wiring sheets such as optical fiber tape cores have a structure wherein coated optical fibers are aligned in a manner leaving no space in between and thus mutually affixed together. These optical fiber wiring sheets allow for composition of smallest structures for wiring coated optical fibers.
As the “last one mile” communication lines are fast changing to optical cables, a process is being needed in which multi-core optical fiber tape cores are branched and connected to individual subscribers. Accordingly, splittable integral optical fiber tape cores have been proposed that are made by arranging multiple optical fiber tape cores (hereinafter referred to as “primary tape cores”) in parallel, and then integrating the primary tape cores by means of secondary covering of the entire tape cores or applying highly peelable coupling resin layers between the parallel primary tape cores (such as those disclosed in Japanese Patent Laid-open Publication Nos. 2002-341205 and 2002-174759).
However, although these optical fiber tape cores can be split into individual optical fiber tape cores by way of splitting the resin layers covering the primary tape cores, the production process for these optical fiber tape cores presents problems. Specifically, these optical fiber tape cores must be produced through a step for producing primary tape cores, followed by another step for coating the primary tape cores with coupling resin. This results in poor production efficiency. Also, it is not possible to split desired numbers of cores and use them as wiring members directly. In addition, producing optical fiber tape cores branching at desired positions requires that bundles of primary tape cores having different numbers of cores be prepared beforehand, which adds to cost. Furthermore, since the resin layer formed on primary tape cores is different from the coupling resin layer, the coupling resin layer peels easily and the broken fragments of coupling resin layer that peel off when the cores are branched can contaminate the surrounding environment.
To connect two devices using optical fibers, the optical fiber must be wired in accordance with the input/output ports on the applicable devices. In actuality, however, the input/output ports on the connected devices often do not have matching positions, in which case the devices cannot be wired using normal optical fiber tape cores because the optical fibers in these optical fiber tape cores are aligned in parallel. If input/output port positions do not match between the devices, the optical fibers of the optical fiber tape cores must be rearranged. Currently, an optical fiber fan-out cable, made of optical fibers that have been wired in such a way that they branch at desired positions, is used to connect input/output ports at desired positions. Alternatively, the optical fibers comprising optical fiber tape cores are separated, and then two pairs of individual optical fibers are connected via connectors or by fusing to rearrange the individual optical fiber tape cores at ends, to make an optical fiber tape again. In the case of an optical fiber fan-out cable, the cable sheath that protects the coated optical fibers is bulky and takes up space. Optical fiber fan-out cables are also less flexible than optical fiber tape cores and thus less easy to work with. In addition, optical fiber fan-out cables provide little advantage over connecting individual single-core optical fibers, and thus congestion of coated optical fibers occurs as the number of input/output ends increases. In the case of the latter method of separating optical fiber tape cores and then rearranging/reattaching them into a tape, the cover of optical fiber tape cores is removed first, and then the single-core optical fibers are individually fused together or attached via connectors. This reduces work efficiency.
As optical fiber wiring members that can align coated optical fibers and thus create desired wiring patterns, optical-fiber wiring plates having two-dimensionally wired optical fibers have been developed. However, these optical-fiber wiring plates have a drawback in terms of size, because they are larger than optical fiber tape cores.
In addition, production of optical fiber tape cores conventionally requires that a wiring pattern of optical fiber tape cores be designed to determine splitting positions in advance. This makes it impossible to split finished optical fiber tape cores into bundles consisting of desired numbers of cores or rearrange the cores.